gomsr

README

gomsr

gomsr is a library for reading from and writing to MSRs. It'll work on any linux machine that supports the msr kernel module. It also supports setting a custom character device location, allowing gomsr to work with utilities such as msr-safe.

A quick and dirty check to see if this will work on your system:

$ ls /dev/cpu/0/msr
/dev/cpu/0/msr

# on some systems, you might need to do this first
$ sudo modprobe msr

This library is a new WIP, and breaking changes should be expected.

Usage

gomsr has no dependencies, and is super easy to use:

//0x198 is IA32_PERF_STATUS on most Intel CPUs

//ReadMSR() takes a CPU and an MSR address
data, err := ReadMSR(0, 0x198)
if err != nil {
	log.Fatalf("Error: %s", err)
}

//You can also write to MSRs
err := WriteMSR(0, 0x401, 0)
if err != nil {
	log.Fatalf("Error: %s", err)
}

//You can also create an msr handler. This is suited for repeated reads/writes

//the MSR() init function just takes a CPU
msr, err := MSR(0)
if err != nil {
	log.Fatalf("Error: %s", err)
}

data, err := msr.Read(0x610)
if err != nil {
	log.Fatalf("Error: %s", err)
}
fmt.Printf("Got 0x%x\n", data)

msr.Close()

Documentation

Index

• func ReadMSR(cpu int, msr int64) (uint64, error)
• func ReadMSRWithLocation(cpu int, msr int64, fmtStr string) (uint64, error)
• func WriteMSR(cpu int, msr int64, value uint64) error
• func WriteMSRWithLocation(cpu int, msr int64, value uint64, fmtStr string) error
• type MSRDev
  • func MSR(cpu int) (MSRDev, error)
  • func MSRWithLocation(cpu int, fmtString string) (MSRDev, error)
  • func (d MSRDev) Close() error
  • func (d MSRDev) Read(msr int64) (uint64, error)
  • func (d MSRDev) Write(regno int64, value uint64) error

Functions

func ReadMSR

func ReadMSR(cpu int, msr int64) (uint64, error)

ReadMSR reads the MSR on the given CPU as a one-time operation

func ReadMSRWithLocation

func ReadMSRWithLocation(cpu int, msr int64, fmtStr string) (uint64, error)

ReadMSRWithLocation is like ReadMSR(), but takes a custom location, for use with testing or 3rd party utilities like llnl/msr-safe It takes a string that has a `%d` format specifier for the cpu. For example: /dev/cpu/%d/msr_safe

func WriteMSR

func WriteMSR(cpu int, msr int64, value uint64) error

WriteMSR writes the MSR on the given CPU as a one-time operation

func WriteMSRWithLocation

func WriteMSRWithLocation(cpu int, msr int64, value uint64, fmtStr string) error

WriteMSRWithLocation is like WriteMSR(), but takes a custom location, for use with testing or 3rd party utilities like llnl/msr-safe It takes a string that has a `%d` format specifier for the cpu. For example: /dev/cpu/%d/msr_safe

Types

type MSRDev

type MSRDev struct {
	// contains filtered or unexported fields
}

MSRDev represents a handler for frequent read/write operations for one-off MSR read/writes, gomsr provides {Read,Write}MSR*() functions

func MSR

func MSR(cpu int) (MSRDev, error)

MSR provides an interface for reoccurring access to a given CPU's MSR interface

func MSRWithLocation

func MSRWithLocation(cpu int, fmtString string) (MSRDev, error)

MSRWithLocation is the same as MSR(), but takes a custom location, for use with testing or 3rd party utilities like llnl/msr-safe It takes a string that has a `%d` format specifier for the cpu. For example: /dev/cpu/%d/msr_safe

func (MSRDev) Close

func (d MSRDev) Close() error

Close closes the connection to the MSR

func (MSRDev) Read

func (d MSRDev) Read(msr int64) (uint64, error)

Read reads a given MSR on the CPU and returns the uint64

func (MSRDev) Write

func (d MSRDev) Write(regno int64, value uint64) error

Write writes a given value to the provided register